System for interconnecting manual and automatic telephone-exchanges



7 a. a. WOLF. SYSTEM FOR IIH'ERCONNECTING MANUAL AND AUTDMATIC TLEPHON EEXCHANGiS.

APPLICAUON HLfD SE91 11. I9I4- mm June 15,- 1920.

2 SHEEIS-SIRET l.

G. D. WOLF.

SYSTEM FOR INIERCONNECTING MANUAL AND AUTOMATIC TELEPHONE EXCHAQGES.

APPuc/moa FILED SEPT- 14. m4.

1,343,4s9, Pamemne 15,1920.

2 snails-sun z.

' 5 EEUPQEZYZ/Z/EZZ FZZZPHE cnoncn n. wot-If, onjcmcaeo, ILLINOIS,ASSIGNOR 'ro KELLooe swrrcr'momn' SUPP]?! CHICAGO, ILLINOIS, ACORPORATION OF ILLINOIS.

,srs'rnn roa' VIVIANULL AND aurona'rrc TnLErnomi-nxcnancns.

I Specification of Letters Patent, Jun 15, 1920.

gm ileptembcr 1i, mi. Serial Re ssues.

To all wklomrit may comm:

Be it known the I, Gnomes D. WoLr, residing at Chicago, county of Cook,and State of Illinois, have invented new and useful Improvements 111Systems for Interconnectand Automatic Telephone-Ely ing Manual which thefollowing is a specichanges, of fication.

connecting main automatic and branch manual exchanges and is moreparticularly to such'systcmswherein the operator at the branch exchangeactuated a calling device in extending connections from the 'manual tothe automatic substations.

In connection with the installation of antomatic telephone systems,operator conexchanges for inter lines are employed. ,operators trolledprivate branch connecting the branch At the private branch eic'hacord'circuits are provided for interconnectand trunk circuits are usedfor interconnec the manual and automa-tic exchanges. 7 en a branch exchange substation toibe connected to an automatic substation theoperator connects ing the local lines,

' one end of a cord circuit tothe calling branch substation and then thecallw ing pluge of the selected cord into a trunk 30 V nding to theautomatic exchange 'after which she a calling device according to thenumber ofthe wanted antomatic substation, to operate the'automaticswitches to extend the call. In systems of this character the operatorupon answer ng a call from a branch substation throws-the listening 'keyto converse with the calling subscriber and one of the features of myinvention resides in a control circuit afi'ected by thethrown listeningkey when the calling'plug is inserted into a trunk jack, to operativelyassociate the operators calling device therewith. In" this way no extramanipulation of a key necessary to connect the calling device.

Another feature of my invention is directed to a control circuit wherebyafter the call has once been extended by the use of the calling deviceand either the listening key has been restored or the calledSllbSCllbeI' has answered, the calling device cannot again be operativly associated with this particular trunk until the establishedconnection has been taken down. In this way I eliminate the possibilityof interference jack e V w w thereto. My invention relates to systemsfor inter e calling device.

qlilrent incidental or intentional actuation of t In the particularembodiment of my invention herein illustrated, I have chosen to use atwo-way trunk circuit but it is to be understood that my invention isnot limited For a better understandin of invention reference 15 to behad to the accompanymg drawings in which all parts are shown at normaland like parts are indicated by likereference characters and in which--Figure 1, part 1, illustrates a cord circuit and two line circuits of aprivate branch exchange togetherwith a trunk circuit ex: tending to anindividual switch capable of extending a connection to anautomaticswitch in the automatic exchange as shown in Fig. 1, part 2, and

Fig. 2 lllustrates diagrammatically the line switches E and .1

Referring now in general to my invention as illustrated in Fig. 1, part1, it comprises a local calling substation A of a well-known type whichis connected by the line limbs 1 and 2 to a line circuit Lwhichcomprises a line relay LR, a signal S and a, jack J. Theprivatebranch cordcircuit C comprises an answering Elug P, and a callingplug P connected byt e heavil marked conductors T and S, and having t econdensers K and K interposed.- The answering endof the cord circuitcomprises an answering supervisory relay AS which controls thesupervisory signal SS and the calling end of the cord circuitC'comprises a callingsupervisory relay CS which controls supervisoryrelay S8. A' listening key LK is provided which when thrown connects theoperators set 0 and a ringing key RK is also shown, which when thrownconnects generator M to ring the called-for substation of a local line.To the right I haveshown a substation B similar to A connected by linelimbs 1 and 2 tIL: a line circuit L similar to that shown at The two-waytrunk circuit D comprises a trunk jack TJ, the terminals of which areconnected by the heavily marked conductors. T and S to'a line switch Eat the automatic exchange. A dial switching relay DS is also included,being energized when a plug of a branch exchange cord circuit isinserted into the jack TJ and the the rela nism.

listening key LK is thrown. Relay DS places the calling device. CB inoperative relation with the trunk circuit D so that'its actuation willenergize the dial connecting relay DR 11 on transmission of each set ofim pulses. switching relay SW is associated with the trunk circuit Dwhich disconnects the incoming call 'signal relay IC and laces thepolarized supervisory re'lag P in bridge of the trunk talking conactors. A supervisory circuit control relay SCR is also associated withthe trunk circuit D and con trols the supervisory circuit leading fromnormal contact 40 to thesignal SS of the cord circuit. Belay SCR' alsocontrols the circuit of the dial switching relay.

An individualswitc h E is associated with each tru'nk'cirouit Dand-comprises a line relay LR ha-cut-ofi relay CO and a motor magnet Mwhich steps the wi are 3, 4', and 5 by the aid of the generator toselect an idle connector F as shown in Fig. 1, part 2. A busy backBB isshown which sends a busy si nal .to the calling subscriber in the eventt at .all the connectors with which the line switch Eis associated. arebusy.

. The connector F which is of the Strowger type and illustrated in Fig.1, part 2, com-.

w a called line'in the selected group. A busy relay BB is associatedwith the connector to connect the busy back BB in case the called lineis busy. A rin ing relay RI is intermittently energized an deenergizedby an interrupter I, to connect the ringing generator M to ring thecalled line and a ringing control relay RCR is energized when the calledsubstation answers to disconnect the ringing'generator M A release relayRR and a release magnet REM areassociated with the connector, the magnetREM being ener ized upon the deenergization of 11 to release the switchmechan off-normal contact Olfl is asso ciated with the connector andassumes its off-normal posit-ion upon the first step of the wiperself-normal. .Side switch arms 9, 10, 11 and 12 are provided and arestopped to their different positions u 'on each restoration of the re ayPV. n automatic substation H is shown to the right of Fig. 1, part 2,being similar to that of A and B, the only difference being that acalling device CD is associated with it; The substa tion H terminates ina line switch E similarto E.

Having described in general the apparatus associated with my invention,the operation will now be described.

Assuming now that two local substations such as'A and B are to" beconnected, the subscriber at substation A removes his receiverenergizing the rela LR by battery through the line relay L normalcontact of the jack J, through the substation A to ground at thejaclr J.The operation of the line relay LR lightsthe signal S and the operatornoting the signal inserts pl P into jack J and throws her listenin keifiaK to ascertain the wants of the cal in subscriber. The insertion ofthe plug into pick J opens the circuit of the line relay R whichdenergizes and efiaces the line signaluS. The supervisory relay AS isener ized from battery through its lower win ing, conductor S sleevecontacts of the plug P and jack J through the substation, tip contactsof the jack J and plug P, upper winding of rela ASto ground energizinthe relay AS w ich prevents the signal SS from lighting. v

Assuming that it is the substation B which is wfliltilldj the operatorinserts the plug P into 'ac thus lighting supervisory signal SS romlground at the third contact of the ack J he operator then throws herringmg key'RK to connect generator M to ring the called-for substationand when the sub scriber thereat answers the calling supervisory relayCS is energized efi'acing super visory si nalSS, The subscribers atsubstations and B upon finishing conversation replace their receiversupon their respective switch-hooks, the circuit for the relays AS and CSthus being opened effectin the li htin of the superv sory signals and Sconnect signals takes down the connection.

Assuming now that a subscriber at the local substation A at the branchexchange wishes to converse with a subscriber at an automatic substationas H, whose li'ne terminates in an automatic exchange, the subscriber atsubstation A removes his receiver from its switch-hook, and theoperation of the circuit C in Fig. 1 part 1 is the same as beforedescribed up to the time the operator plugged into the jack J The 0enter having t rown her listening ke L to ascertain the wants of thecalling su scriber and noting that it is the automatic substation Hwhich is wanted, she inserts the plug P into the trunk jack TJ with herlistening key throwninto its alternate osition so as to place thecalling device D in operative relation with the trunk circuit D. Thelisteningkey LK being thrown, the ground at its alternatecontact2lclosesacircuit for the relay DS traced from ground at thealternate contact 24 of LK, the third contacts of the plug P and jackTJ, normal contact he operator noting the dis-,

m e est relay SW tracedfrom battery through its i 25, through thewindinfiof relay us to batenergizing relay S. he closingof alternatecoutact 50 of reab ishes an energizing circuit for windin closedcontacts 29, 30, of the trunk jack T conductor 31, alternate contact 50,normal contact? 9, to ground at contact 34, energizing 'switchin relaySW which closes a locking circuit or itself from battery -:throu h itswinding, closedcontacts 29, 30,

I, of jac TJ, alternate, contact 34 to ground,

" this relay remaining eneliglzed as long as the rela J. Theswitchingbeing brought about as follows: Upon the said energization ofrelay SW its alternate contact 37 is losedestablishing an energizingcircuit for line relay LR of the line switch E, traced from batterythrough the winding of relay LE the wiper 4, conductor T; normalcontact13, the normal contact 14, tip conductor T of the trunk D, conductor 36,alternate contact 37, conductor 38, the

winding of relay PSR, conductor S normal contacts 17, 18, conductor S toground at wiper 5. Theenergization of relay LR closes an energizingvcircuit for cut-oil relay CO from ground at alternate contact 19 ofrelay LE normal contact 20 of the ofl'norinal contact ON, through thewinding of relay CO to batter Upon energization of relays CO and L anenergizing circuit for the motor magnet MM is established at alternatecontact 23 of relay LR? traced from the ungrounded pole of the generatorM through the winding of the motor magnet MM, alternate-contact 22 toglfl li lld he motor magnet is energized and steps the wipers 3, 4, and5 of the individual switch E to select contacts of an idle connector.Upon the first step of the wipers of the switch E ofl normal, theoil-normal contacts ON assume their alternate position and open theinitial energizing circuit of the relay (0, but the relay CO remainsenergi'zed as long as the wiper 3 encounters grounded contacts 3 but assoon as the un grounded contact is encountered, the relay 0' deenergizesand disconnects the motor magnet MM to prevent further stepping of thewipers 3, 4 and 5. Relay LR being slow retains its armature attracteduntil a holding circuit is provided by the selected connectoras will bedescribed.

An idle connector as F having been selected by the switch E, theinterrupter relay IR which is bridged across the lineconductors of theconnector '1' operates, its circuit bein traced from batterythrough'itsuppler win ing, normal contact 35, conductor contact-4, wiper4, conductor T, normal contact 13, normal contact 14, conductor Tconductor 36, alternate contact 37, conductor 38, through windings ofthe polarized supervisory relay PSR, conductor 8, normal contact 17,normal contact 1'8,-conducto'r S wiper 5, contact 5 conductor Sf,normal,

contact 39 andfthrough' lower winding of relay IR toIground; ,Thebattery flow vfor the polarizedrela PSR is in-such direction that saidrelay SR does not operate but relay SCR bein back because key LK andrelay D8 are still operated ground at normal contact '40 does not affectthe cord circuit.

The operation of relay, IR closes an energizautomatic substation is 45the operator actuates the calling device Cl) to send four impulses overthe line to operate the selected connector F. As the calling deviceleaves its normal position, contact 26 associated therewith assumes itsalternate position energizing the dial connecting relay DR by currentfrom battery through the winding of relay DR, alternate contact 27 ofrelay Db (which was energized when plug P was inserted into trunk jackTJ. and the listening key thrown) conductor 28, alternate contact 26 toground. Relay DR remains energized during each operation of the callingdevice closing its alternate con Assuming that the number of the calledtacts 83 and 84- to connect the calling derelay IR, alternate contact42, winding of relay SR, conductor 43, winding of vertical magnet VMthrough the side switch arm 10 to battery. The relay SR being a slowacting relay maintains .its armature attracted during the ra fiidinterruptions of its circuit by the relay 1 a but the vertical magnet VMbeing quick-acting is responsive to said impulses and steps the wipers6, 7, and 8 of the Y armature of P attracted.

After thefirst set of impulses relay PV denergizes having its circuitopened at alternate contact 100 upon the deenergization of reiay SR, andmechanically steps the side switch arms 9,10, 11' and 12 to their secondposition to engage contacts 44, 45, 46 and 47. The side switch armengagigig the contact 45 places the rotary magnet in series circuit withthe relay SE to receive v impulses to cause the next set of impulses.The operator now alctuates the callin device CD to send five ve oerations of the interrupter. relay. IR. pon the first deenergizationf ofreiayIR-ythe relay SR and the rotary magnet RM which are connected inseries, are energized from ground at nor.-

mal contact 41., alternate contact 42, winding of SR alternate contact101, the winding of relay ll-M, side switch'contact 45, wiper 10 tobattery. The rotary magnet also being quick acting is responsive to thequick interruptions and steps the wipers 6, 7 and 8.

tothe fifthcontacts of the fourth level which are the contacts of thewanted line. The olf-normal contacts 0N assume their alternate positionupon the first step of the switch movement.

After the last set of impulses the operator restores the listening keyLK of the cord circuit Ciremoving the ground from the energizin circuitof the rela DS of'trunk circuit Upon the deenergization of the relay DSa circuit is closed for the signal control rela SCR traced from batterythrough the win 'ng'of the relay SCR, conductor 48, alternate contact49, normal contact 50, conductor 31, alternate contact 34 to ground. Therelay SOB upon energization, closes a lockin circuit for itself tracedfrom battery throng its winding, alternate contact 51, conductor 31,alternate contact 34 of relay SW to ground. The closin of the alternatecontact 25 of relay CR places a round upon the third contact of the jackJ, this round closing an ene izing circuit for t esupervisory signal Straced from battery,-lamp SS normal contact 52,

normal contact 24, third contacts of the plug P and jack TJ, alternatecontact 25, normal round, lighting the supervisory signal S whichremains lighted until the subscriber at the called-for substationanswers.

It will be noted that after the operator has once restored her key LKafter the transmission ofthe impulses, due to locking up of SCR anysubsequent manipulation of the listening key does not operate relay DSand therefore it is impossible to operatively connect the calling deviceagain. This prevents intentional or accidental interference withestablished connections.

Ualled line idle.

After the last set of impulses the private relay PV deiinergizes havinghad its circuit opened by the deenergization of SR, to step the sideswitch arms 9, 10, 11 and 12 to their third position to engage contacts53, '54, 55

and 56. The arm 10, engaging the contact 54 closes an energizin circuitfor the rin ing relay RI traced rombattery throng the side switch arm10, conductor 57, normal contact 58 of relay RCR, conductor 59 throughwinding of relayRI, through inter. rupter I to ground. The relay RIisenergized and deiinergized to connect the ringing generator M to thealternate contacts 60 and 61 of relay RI to intermittently ring the callbell at the called-for substation H. \Vhen the subscriber at substationH removes his receiver from the switch-hook in reisponse to his callbell, the reversing relay R operates by current over the called line,

circuit being traced from battery through lower winding of reversingrelay RV, normal contact 62, conductor S normal contact 61, wiper 8,contact8; line limb 1 through the substation, line limb 2", contact 7wiper 7, normal contact 60, conductor T, I

of relay PSR, conductor 38, alternate contact 37, conductor 36,conductor T, normal contact 14, normal contact 13, conductor T, wiper 4,contact 4, conductor T alternate contact 35, lower winding of relay IRtoground. The contact 40 of relay PSR thus assumes its alternate positionopening the circuit of the supervisory lamp SS of the cord circuit C-notifying the operator at the branch exchange that the called automaticsubstation has answered. 7

The operationof the reversin relay RV also closes an ener 'zing circuitor the ringing control rela CR traced from batter through the winding ofthe relay RCl alternate contact 64, conductor 65, the side switch arm 9to ground at the contact 53 Release. 7

V p After conversation has been completed the subscriber at calledsubstation H re- "places -his receiver upon its switch-hook circuit ofthe relay 7 opening the ener 10 RV, the relay Ra denergizing and againcausing the reversal ofbattery through the windings'of relay PSR theground upon the third contact 0 the jack TJ again lighting thesupervisory lam SS of the cord circuit (1 and thus noti 'ng theoperator' that the called; subscriber has hung up.

, lighting lamp release magnet RE The subscriber at'the substationhaving replaced his receiver opens'the circuit of the rela AS of thecord circuit C s and the operator noting the two lighted lamps withdrawsthe plugs P and P from-the jaclesJ'and J eifacing the lamps. The removalof plug P also oiae ns the circuit for the switchlng rela S throughcontacts 29 and 30. of the jach TJ and the denergization of relay SWcauses deiinergization of relay SCR. The deia'nergization of relay SWalso opens the energizing circuit of relay IR of the coin nector F atalternate contact 37, the said [relay IR deenergizing and opening thecir- RR which operates restoring the connector F. The removal of groundat alternate contact 69 of RR permits the restoration of LR of switch Ewhereupon its normal contact 19 is closed energizing rela CO. Relay COenergizing and relay 1R restoring, both retaining pawls are withdrawnallowing the wipers o restore to normal as will be clear from aninspection of Fig. 2.

From the above description it may be seen that the release of theautomatic apparatus is underthe control of the operator at the localexchange and by the removal of the plug from the trunk jack theautomatic apparatus is restored to normal.

Called line busy. 7 Assuming that the operator has operated cuit' forrelease rela the calling device to send the last set of impulses, whichare five in number, to select the wanted line of the called substation.Now if the called substation 'is busy a round appears'at its privatecontact 6 irom the alternate contact 19 of the individual switch E. Thisground will establish an ener ing circuit for the busy relay BR traced rdm battery through the upper winding of relay BR, the side switchcontact 44, side switch arm 9 which is now in its second position, theconductor 68, private wiper 6, contact 6 to ground at alternate contact19 of the line relay LR 'of the individual switch E The busy relay BRlocks up from ground at alternate contact 69 of relay RB, conductor 70,alternate contact 71, lower windingof relay BR through the relay PV tobattery. Due to the relay SR being a slow acting relay, it remainsenergized momentarily preventing the private I relay PV from releasinguntil another circuit is established for it in series with the lowerwinding of the relay BR. The-relay PV remainin energized does not step.the side switch wipers, they remaining in their second position. Thisconnects the busy back BB through the alternate contact 72 of relay BR,side switch contact 47, the side switch arm 12, conductor S and uponrestoration of key LK said signal continues back to the callingsubstation notifying the calling subscriber that the called line isbusy.

he restoration of the operators listeningf key causes the operation ofrela S and SCR-and lighting of SS as fore. The replacing of the callingreceiver lights SS. Therefore the operatorwithdraws the plugsde'nergizing SW and SCR as before followed by the dener 'zation of IReffecting the restoration 0 the connector and line switch E as will beclear from the foregoing description.

Automatic to branch exchange. N ow assuming that the automaticsubscriber at H wishes to call a local substation terminating at theprivate branch exchange, he removes his receiver which act energizesline relay-LR of the individual switch E.

The line relay LR operating closes an energizingcircuit for cut-ofl'relay G0 which in turn closes an energizing circuit for motor magnet MMwhich steps the wipers 3*, 45*, 5 to select an idle connector as F in amanner which will be apparent from the previous description.

Assuming now that the automatic substation is calling the number 43which is the number of one of the trunk linestcrminating at the branchexchange, the calling device is operated to send four impulses to stepthe wipers of the selected connector vertically to the fourth row ofcontacts. He then operates the dial to send three impulses of currenttoestep the wipers to the third contact in the fourth row which are thecontacts 73, 74, 75 associated with a trunk circuit such as D. When theconnector wipers stop on the contacts BS80- ciated with the idle trunk,a ground is placed upon the private contacts 73 to opcrate the cut-offrelay C0 of the line switch E to remove the trunk control thereof.

Assuming that the trunk circuit D is in an idle condition, ringingcurrent is applied from the ringing generator, and operates relay IQ ofthe trunk circuit D over a circuit traced from ringing generator of theconnector, the connector, normal contact 60,

' wiper 7, contact 74:, conductor 76, normal tact 75, wiper 8, alternatecontact 61, back to the ringing generator. The relay 1C is energized andlocks u over a circuit traced from batter throng the lower winding ofthe relay C, alternate contact 79 normal contact 34, to ground. Thiscloses a circuit for the trunk call signal TS traced from batterythrough the lamp TS, alternate contact 7 9, normal contact 34 to ground.

The operator at the branch exchange observin the signal TS inserts ananswering plug into the trunk jack TJ operating the switchin relay SW,the circuit being traced from Eattery through the winding of relay SW,closed contacts 29, 30, conductor 31, normal contacts 50, 49, 80,alternate contact 79, normal contact 34 to ground. The switching relaySW upon energization closes a locking circuit for itself traced frombattery through the winding of relay SW, contacts 29 and 30 andalternate contact 34 to ground. The contact 34 of relay SW being a makebefore break contact gives the switching relay SW a chance to lock upthrough its own contact 34 to ground before the initial energizingcircuit is broken. The relay SCR is energized upon energization of therelay SW, the circuit being traced from battery through the Winding ofrelay SCH, alternate contact 49, normal contact 50, conductor 31,alternate contact 34 to ground. The relay *S'CR closes a locking circuitfor itself traced from battery through its winding, alternate contact51, alternate contact 34 to ground.

Upon energization of relay SW the circuit of relay IC is interrupted toefface signal TS and the closing of alternate contact -37 of SW bridgesthe polarized supervisory relay PSR across the trunk. Current throu hrelay RV now flows through relay P R in such direction as to attract thearmature of PSR and interrupt normal contact 40, to prevent lightingsupervisory lamp SS. Re-

. lay RV also energizes and operates relay RCR to prevent furtherapplication of ringing current in a manner as before described. heoperator now throws the listening key LK of the cord circuit C andassuming that it is the local tele hone A that is wanted, she insertsplug 1 into the jack J lighting the supervisory signal SS then throwsthe rigging key RK to connect ringing generator to ring the called-forsubstation A.

The subscriber at A in answering, energizes the calling supervisoryrelay CS open- She.

ing the circuit for lamp SS The two substations are now connected in aconversational circuit. 1 7

Upon completing conversation the' subscribers restore their receiversupon their respective switch-hooks, the restoration at the calledsubstation A effecting the deenergization of relay CS and lighting thesignal 88, The replacing of the receiver at the calling substation Hinterrupts the circuit for the associated impulse relay IR whichrestores closing a circuit for the re lease magnet REM followed by therestoration 'of the connector F. Upon the release of the connector,ground is removed from its test conductor 102 b the restoration ofrelease relay RR so t at the line switch E restores to normal in amanner which will be clear from the foregoing description.

The said restoration of the connector also removes ground from theprivate or test contact 73 of the trunk individual switch E whereb itscut-oil relay GO restores. This establis es an energizing circuit forthe line relay LR which brings about the operation of the trunk switch Dto select an idle con* nector F whereupon the polarized relay PSR isrendered inert and establishes a circuit for the supervisory signal SS.The forego' ingyoperation is brought about as follows:

p on said restoration of relay G0 a' circuit is established traced frombattery through the winding of LB, wiper 4 and its normal contact,conductor T normal contact 13, conductors T 36, alternate contact 37 thewinding of PSR, normal contact 17, normal contact 18, conductor S andwiper 5 to ground. The direction of current flow through relays LR andPSR- is such as to restore relay PSR andthe energization of LR isfollowed by the energization of CO as before described. Therefore normalcontacts 13, 18 of C0 are interrupted opening the circuit for PSR andrelays CO and LR being ener ized switch E advances its wipers until anid upon relay CO immediately restores connecting the impulse rela IR ofthe selected connector in circuit wit the polarized relay PSR, thecurrent flow beingin such di rection as to maintain relay PSR inert.Normal contact 40 of the polarized relay is thus maintained closedestablishing a circuit for superviso signal-SS and therefore theoperator withdraws plugs P and P from the jacks. The withdrawal of thele connector is reached. There-,

, tening ke calling device is operatively disassociatedfrom the trunkshould the called subscriber respond prior to the restoration of thelis- It will be remembered that after a ca 1 has been extended by theuse of the calling device, the operator restores her listening key whichrestores the dial switching-rela DS and causes the energization of,

relay S R so that any furthermanipulation of the calling device duringan established connection is without effect. It may sometimeshap n thata called subscriber will reof the 'polarized nelay which occurs when thesubscriber answers efl'ects the closure of its alternate contact 10causing the energizetion of relay SCR so that the interruption of itsnormal contact 25 restores relay DS. Re lay SCR also locks up throughits alternate contact 51 in a manner as already set forth. A subsequentrestoration of the operators listening key will therefore have no effectupon the trunk circuit relays. The circuit of relay DS having beeninterrupted at norcmal contact 25, it will be apparent that it isimpossible to again associate the calling device with the cord circuitby the manipulation of the listening key until the connection has beentaken down.

Having described my invention, what I claim as new and desire to secureby United States Letters Patent, is:

1. A telephone system comprising a main automatic exchange, a branchoperator controlled excha ge, an operators cord circuit forinterconnecting the branch substations, a trunk circuit extending fromthe branch to the main exchange, a calling device incapable of normaloperative association with the trunk circuit, a relay for operativelyassociating said calling de vice with said trunk circuit, a listeningkey for the cord circuit, and means responsive to the connection of thecall plug of the cord with the trunk circuit an the operation of thelistening key for rendering said relay capable of being operated tooperatively associate said calling device with the trunk circuit.

2. A telephone system comprising an operators position having a cordcircuit for interconnecting telephone lines, a trunk circuit extendingfrom the operators position to an automatic exchange, a calling devicefor the trunk circuit incapable of normal operative associationtherewith, a relay for associating said calling device with said trunkcircuit, an operators key for the cord circuit,

and the operation of said key for rendering said relay capable of beingoperated to operatively associate said calling device with the trunkcircuit. 3. A telephone system comprising an operators position having acord circuit for interconnecting telephone lines, a trunk circuitextending from the operators position to an automatic exchange, acalling device for the trunk circuit incapable of normal operativeassociation therewith, an operators key for the cord circuit, meansresponsive to the connection of a' terminal of the cord with the trunkcircuit and the operation of said key for rendering said calling devicecapable ofcperative association with the trunk circuit, and meansresponsive to each operation of the calling device for operativelyconnecting it with the trunk circuit.

4. A telephone system comprising a cord circuit, a trunk circuit forconnecting said trunk circuit and said key is operated for effecting onestep in operatively connecting said calling device-with the trunk, andmeans responsive to the operation of the calling device for operatingthe other one of said relays for operatively connecting the callingdevice with the trunk.

A telephone system comprising a cord circuit, a trunk circuit forconnecting said cord with an automatic exchange, a calling device forthe trunk circuit, means controlled by the operator for operativelyassociating said calling device with the trunk circuit, automaticswitches responsive to said calling device for extending the trunkcircuit to a called line, and means operated u on response from thecalled substationor 0peratively disassociating said calling device andtrunk circuit.

6. A telephone system comprising a cord circuit, a trunk circuit forconnecting" said cord with an automaticexchange, a calling device, anoperators key for the cord circuit, means responsive to the actuation ofsaid key and the connection of said cord with the trunk for operativelyassociating said calling device with the trunk circuit, and meansresponsive to subsequent restoration of the key to operativelydisassociate said calling device and the trunk circuit and prevent theiroperative association while said cord and trunk remain connected.

7. A telephone system comprising an operaters cord circuit provided withan operators key, a plurality. of trunk circuits trunk circui 1-,

accessible to said cord circuit and extending to automatic switches inan automatic exchange, a calling device common to said trunk circuits, arelay for each of said trunk circuits for operatively associatin saidcalling device with its respective trun circuit, means for connectingsaid cord circuit with one of said trunk circuits, a circuit for therelay of the connected trunk circuit including contacts of saidoperators key, and means for operatin said relay to operativelyassociate the calling device with said trunk circuit.

8. AL telephone system comprising an op-l.

erators COIdeClIT-Jlllt rovided with an operators key, a plum tyof-trunk'cucuits ac essible to said cord circuit and extending toautomatic switches in an antomatic' e1:-

change, a calling device common to said trunk circuits, a relay for eachof said trunk circuits for operatively associating said call ing devicewith its respective trunk circuit,

means for connecting said cord circuit with one of said. trunk circuits,azc'ircuit for the relay of the connected trunk cii'cuit includingcontacts ofusaid operators key, and

, means ior operatfing'i- 'said relay to opera-v tively associate thecalling device with Said.

trun circuit,-an d a subscriber controlled relay'for said ltrjmk circuitfor operatively dis'associati calling device and said 9. Atelephciiesysufi com rising an operators cord=cirfli1tprovided with anoperators key,a plur i accessible to said cord circuit ,and extending toequipment inan automatic exchange, a calling device common to saidftrunkcircuits, electromagnetic means for each of said trunk circults foroperatively associating said calling device with said trunk circuits,means for operatively disassociating said callingdevlce from a connectedtion of the subscriber from the trunk circuit. V. i

11. A telephone system inciuding a two way trunk circuit extending froma manual exchange toanautoniatic exchange, a calling device, means foroperatively associating said calling device with said trunk circuit whensaid circuit is used to extend a said trunk circuit;

tyof trunk circuits call in one direction, and means for preventing anoperative association of said calling device and said trunk circuit whensaidtrunk circuit is used toextend a call in the opposite direction.

12. A telephone system comprising an operators cord circuit providedwith an operators listening kc a trunk circuit, a calling deviceassociate with said trunk circuit but normally disconnected therefrom,means for connecting said ,cord circuit with said trunk circuit,electromagnetic means for op-. eratively associatingsaid calling devicewith said trunk circuit, a circuit for said electro-v magnetic meansincluding contacts of said operatbrs listening-key, and means foroperating saidelectroma etic means to operatively associate 'saicf 13. Atele hone system comprising an operators cor circuit; erators listeninglie trunk-circuit, a calling device associatediwitlia -said trunkcircuitbut normally disconnected therefrom, means for connecting'fsaidcord circult with said trunk circuit,electrom etic means for operativelyassociating sai callmg device with said trunk circu t, a circuit forsaid electromagnetic means inciudin contacts of sa'idoperators listeningkey, an means for operating said electromagnetic calling device andvidedflwith an opmeans tooperativelflassociate said calling 7 device andsaid circuit, and means responsive to an operation of said operators keyto disassociate said calling device and said trunk circuit and prevent areassociation of said calling device and said trunk circuit while saidcord circuit is operatively connected to said trunk circuit.

14. A telephone system comprising a trunk circuit extending to anautomatic-exchange, a rotary manually operable calling device for saidtrunk circuit, and a relay individual to the said trunk circuitenergized responsive to each operation of said calling device whendialing a number for directl connecting said calling device to said truncircuit.

15. A telephonesystem including an operators position, a plurality oftrunk circuits extending from said operators position to automaticequipment in an automatic exchange, a calling device common to saidtrunk circuits, electromagnetic means individual to each of said trunkcircuits for operatively associating said calling device with said trunkcircuits, and means responsive to an operation of said calling devicefor operating the electromagnetic means of a trunk circuit tooperatively associate saidcalling device with said trunk circuit priorto an operation of said automatic equipment.

16. A telephone system including an operators cord circuit, a pluralityof trunk circuits accessible to said cord circuit and extending toequipment in an automatic exchange, a calhng device common to said trunkcircuits, and means res nsive to the a connecting of said cord circuitwith one of called line, 'andmeans operated upon re spouse from thecalled substation to .operatively disassociate saidcalling device andsaid trunk circuit and for preventing a reassociation of said callingdevice and said calling circuit while said link circuit is connected tosaid trunk circuit. I

18. A telephone system including a trunk circuit extending from a manualexchange to an automatic exchange, a calling device, electromagneticmeans individual to said trunk circuit for operatively associating saidcallin device with said trunk circuit, and subscriber-controlled meansfor operatively disassociating said calling device from said trunkcircuit.

19. Atelephone system including a trunk circuit extending to anautomatic exchange,

\ a calling device, an operators cord circuit provided with a listeningkey, and electromagnetic means responsive to an actuation of saidlistenin key and an operation of said calling demos for operativelyassociating said calling device. and said trunk circuit.

20. A telephone system including an operators link circuit, a trunkcircuit, a calling device, manual means for connecting said trunkcircuit directly tosaid link circuit, and means responsive to a'contr'olexerted at said link circuit and an operation ofsaid calling device foroperatively connecting said calling device with said trunk circuit.

21. A telephone system including an 0perators link circuit provided witha key, a trunk circuit, a calling device, a simple relay adapted uponencr "zation to operativel associate .said calling evicc with said truncircuit, and means de endent upon an actuation of said ke an anoperation of said calling device or actuating. said relay to operativelyassociate said calling device with said trunk circuit.

22. A telephone system including a trunk circuit, a caling device, arotary manually operable settintg member for said calling device, a pair0 ontacts adapted to .be actuated each time said settin member isoperated, 'a key, a relay in ividual to sald trunk circuit forconnecting said calling device with said trunk circuit, and a circuitfor said relay controllable by said key and said contacts.

23. A telephone system including a trunk circuit, an oiperators rotaryimpulse-sending "device, 0 -normal springs ada ted to be closed uponeach actuation of saidimpulsesending device, and a relay individual tosaid trunk circuit provided with a circuit including said contactsadapted to be energized' upon each operation of-said device forassociating said device with said trunk circuit.

24. A telephone system including a trunk circuit, an operatorsimpulse-sending device, a relay responsive to an o eration of saiddevice for associating said evice with said trunk circuit, andsubscriber-controlled means for disassociatingsaid sending de vice andsaid trunk circuit.

25. A telephone system including an operators link circuit provided witha key, a calling device, a rotary manually operable setting member forsaid calling device, oil'- normal springs adapted to be actuated uponeach operation of said setting member, and

a relay individual to said trunk circuit controllable by said key andthe off-normal contacts of said calling device for operativelassociating said calling device with said lin circuit.

26. A telephone system including an op erators link circuit providedwith a key, a trunk circuit connected to said link circuit, a callingdevice, means controlled by said key and said calling device forconnecting said calling device with said trunk circuit, a numericalswitch, and a non-numerical switch for connecting said trunk circuit tosaid numerical switch.

27. A telephone system including operators cord circuits provided withlistening keys, trunk circuits, a calling device commen to said trunkcircuits, manual means a for connecting one of said cord circuits tosaid trunk circuit, means for said trunk circuit operable in re sponseto an operation of the listenin key of said cord circuit for associatingsai call-V ing device with said trunk clrcuit.

and electromagnetic:

device for connecting said device to said a trunk circuit.

29. A telephone system including an 0 erators link circuit, a trunkcircuit exten ing from a manual exchange to an automatic exchange, acalling device, means responsive to an operation of said calling deviceto connect said calling device with said trunk circuit said-meansincluding a rela provided with a circuit the closure of whic iscontingent u on an operation of said calling device an the connection ofsaid link circuit to said trunk circuit.

30. A telephone system including a trunk circuit ternimating in a manualconnection terminal and in an automatic switch, an 0 crators callindevice, and a rela adapte when 0 crates to connect the sai callingdevice wit said trunk circuit and to operate said automatic switch.

31. telephone system including a trunk circuit terminating in a manualconnection terminal and in an automatic switch, acalling device, a relayindividual to said trunk circuit for connecting said calling device'tosaid trunk circuit, and means responsive to the connection of saidcalling device to said trunk circuit for operating said automaticswitch. 7 r

32. A telephone exchange system including-a trunk circuit terminating ina manual connection terminal and in an automatic switch, a key, acalling device, a relay, means for o crating said relay to connect saidcalli'ng evice to said trunk circuit responsive toan operation of saidcalling device and said key, said automatic switch being operableresponsive to the connection ofsaid calling device with said trunkcircuit.

3. A telephone system includingan operators cord circuit provided with akey, a trunk circuit, a calling device, a pairof relays for said trunkcircuit, means for operatin one of said relays responsive to an actuaton of said key, thereby reparing a circuit for the other of said re a s,and means responsive to an actuation 0 said calling device to operatesaid other relay to operaators cord circuit trunk 01!C\11i38, a cal ingdevice common to said trunk circuits, and electroma 61310 and tivelassociate said calling device with said trun cllclfit.

84. A telephone system includin an 0 errovided Willi a Eey,

means individual to each of said trun circuits and responsive to anactuation of said calling device to connect said calling device with atrunk circuit...

35 A telephone system including an open ators cord circuit, trunkcircuits, a calling device common to said trunk circuits, means forconnecting said operators cord circuit many of said trunk circuits, andmeans individual to a trunk circuit 0 erated respon sive to an actuationof said calling device for connecting said calling device to the trunkcircuit to which said cord circuit has been connected.

36. A telephone system including an operators cord circuit, trunkcircuits, a calling device common to said trunk circuits, means forconnecting said operators cord circuit to any of sand trunk circuits,means individual to a trunk circuit operated responsive to an actuationof said calling device for connecting said calling device vto the trunkcircuit to which said cord circuit has been connected, and means forpreventing a subsequent actuation of said calling device from againconnecting said calling device to said trunk circuit,

Si ed by me at Chicago, county of Cook, tate of Illinois, in thepresence of two witnewes.

GEORGE D. WOLF.

Witnesses Gnonon E. MUELLER, B. OBnmN.

